Industrial robots are conventionally provided on production lines of a factory in manufacturing industries. In order to make such the industrial robot accurately perform the same repetitive task on conveyed workpieces, it is necessary to fix the workpieces at a determined location each time. In order to make one production line correspond to the fixation of various kinds of workpieces, a workpiece positioning device disclosed in Japanese Laid-open Patent Publication No. 2002-263965 employs an orthogonal three-axis mechanism.
In the case of the auto industry, for example, because a workpiece such as a body of an automobile is larger than a workpiece positioning device in many cases, four to eight workpiece positioning devices are usually used to fix one workpiece. Therefore, a production line, on which a plurality of orthogonal three-axis workpiece positioning devices jointly performs a work task, has a problem in that it is difficult to save a space and thus to reduce a footprint for a process area.